In various attempts to relate the behaviour of highly-elastic liquids in complex flows to their rheometrical behaviour, obvious candidates for study have been the variation of shear viscosity with shear rate, the two normal stress differences N-1 and N-2, especially N-1, the extensional viscosity, and the dynamic moduli G' and G ''. In this paper, we shall confine attention to 'constant-viscosity' Boger fluids, and, accordingly, we shall limit attention to N-1, eta(E), G' and G ''.
We shall concentrate on the "splashing" problem (particularly that which arises when a liquid drop falls onto the free surface of the same liquid). Modern numerical techniques are employed to provide the theoretical predictions. We show that high eta(E) can certainly reduce the height of the so-called Worthington jet, thus confirming earlier suggestions, but other rheometrical influences (steady and transient) can also have a role to play and the overall picture may not be as clear as it was once envisaged. We argue that this is due in the main to the fact that splashing is a manifestly unsteady flow. To confirm this proposition, we obtain numerical simulations for the linear Jeffreys model. (C) 2010 Elsevier B.V. All rights reserved.
- boger fluids
- constitutive modeling
- computational rheology
- free-surface flows